CN104677287A - Micro-scale measurement device and method adopting three-core optical fiber grating probe and based on optical fiber ring laser - Google Patents

Abstract

A three-core fiber grating probe micro-scale measurement device and method based on a fiber ring laser belongs to the field of precision instrument manufacturing and measurement technology; the device includes a pump source, a wavelength division multiplexer, an erbium-doped optical fiber, a saturable absorber, An optical switch, an external reference grating, a three-core fiber grating probe, a computer, a spectrum analyzer, and a pump source are connected to a ring cavity composed of an erbium-doped fiber, a circulator, a coupler and an isolator B through a wavelength division multiplexer, and the coupling The device is connected with a spectrum analyzer and a computer through an isolator A to form a path; the method is that the computer controls a multi-channel optical switch to switch the optical path, and the spectrum analyzer is used to measure the three-core fiber grating probe and the external reference grating respectively as a laser wavelength selection device. The laser wavelength output by the fiber ring laser uses a differential data processing algorithm to realize two-dimensional micro-scale measurement without temperature coupling; the invention has the characteristics of integrated sensing and energy supply, compact system and high sensitivity.

Description

Micro-scale measurement device and method for three-core fiber grating probe based on fiber ring laser

technical field

The invention belongs to the technical field of precision instrument manufacturing and measurement, and in particular relates to a micro-scale measuring device and method for a three-core fiber grating probe based on an optical fiber ring laser.

Background technique

With the continuous development of the aerospace industry, automobile industry, electronics industry and cutting-edge industries, the demand for precision and tiny components has increased dramatically. Due to the limitations of the space scale and the shadowing effect of the micro-components to be measured, as well as the influence of the measurement contact force, it is difficult to realize the precise measurement of the micro-component scale, especially the measurement of the depth of the micro-cavity components is difficult to increase, which has become a constraint to the development of the industry. "bottleneck". In order to achieve smaller size measurement and increase the measurement depth, the most widely used method is to use a slender probe to penetrate into the inner cavity of tiny components for detection, and measure the tiny inner dimensions at different depths by aiming at the signal. Therefore, at present, the precise measurement of the size of tiny components is mainly based on the coordinate measuring machine combined with the aiming signal detection system with a slender probe. Since the development of the coordinate measuring machine technology has been relatively mature, it can provide precise three-dimensional space movement, so the aiming trigger The detection method of the type probe becomes the key to the design of the detection system for small component sizes.

At present, the main means of measuring the size of tiny components include the following methods:

1. Professor Tan Jiubin and Professor Cui Jiwen of Harbin Institute of Technology in China proposed a probe structure based on dual optical fiber coupling. The two optical fibers are connected through the fusion ball at the end, and the fusion ball is used as the probe, and a longer optical fiber is introduced into the light. A short lead-out light overcomes the limitation of measuring depth by micro-bead scattering method, and can realize accurate aiming when measuring micro-deep holes with a diameter not less than 0.01mm and a depth-to-diameter ratio not greater than 15 _: 1. Although this method overcomes the shadowing effect to a certain extent, the light energy of the reverse transmission achieved by the coupling sphere is very limited, and it is difficult to further improve the measurement depth.

2. The National Institute of Standards and Technology of the United States uses a probe with a single optical fiber measuring rod combined with a micro-optical bead. Through optical design, the imaging of the optical fiber measuring rod is magnified by about 35 times in the two-dimensional direction, and two area array CCDs are used to distinguish and receive the two-dimensional The image formed by the optical fiber measuring rod in the direction, and then the contour detection is performed on the received image, so as to monitor the tiny movement of the optical fiber measuring rod during the measurement process, and then realize the trigger measurement. The theoretical resolution of the detection system can reach 4nm , the probe diameter of the detection system is Φ75μm. In the experiment, the aperture of Φ129μm was measured, and the probability value of the expanded uncertainty reached 70nm (k=2), and the measurement force was in the order of μN. This method has high detection resolution and high measurement accuracy, and the probe used is easy to miniaturize, and can measure micropores with a large depth-to-diameter ratio. However, in the method to detect the two-dimensional touch displacement of the optical fiber measuring rod, two sets of imaging systems must be used, resulting in a complex system structure and a relatively large amount of calculation of measurement data. These factors lead to poor real-time performance of the detection system and a relatively complex system composition.

3. The Swiss Joint Metrology Office has developed a new type of coordinate measuring machine dedicated to the traceable measurement of small structural parts with nanometer precision. The measuring machine adopts a new type of contact probe with a bending hinge structure based on the principle of parallel kinematics. This design can reduce the moving mass and ensure low stiffness in all directions. It is a probe with three-dimensional space structure detection capability. This sensing structure has a measuring force below 0.5mN and supports replaceable probes with diameters as small as Φ100μm. The detection system incorporates a high positional accuracy platform developed by PhilipsCFT with a positional accuracy of 20nm. The standard deviation of the measurement repeatability of the measurement system reaches 5nm, and the uncertainty of the measurement result is 50nm. The structural design of this method is complex, and the measuring rod is required to have high rigidity and hardness, otherwise it is difficult to realize effective touch displacement sensing, which makes it difficult to further miniaturize the measuring rod structure, and the depth-to-diameter ratio of the measurement is also restricted. The resolution of the system is difficult to further improve.

4. Professor Cui Jiwen and Yang Fuling from Harbin Institute of Technology in China proposed a micropore size measurement device and method based on FBGBending. High-frequency laser interferometer length measurement device can obtain the micropore size of different sections. When the micro-scale sensor of this method touches the deformation, the main stress of the probe does not act on the fiber grating, and the resolution of the system is very low, which is difficult to further improve.

In summary, in the current micro-size and coordinate detection methods, probes made of optical fibers have attracted widespread attention due to their small probe size, small measurement contact force, large measurement depth-to-diameter ratio, and high measurement accuracy. Its unique optical and mechanical properties realize the precise measurement of tiny dimensions at a certain depth through various methods. The main problems with current measurement methods are:

1. It is difficult to further improve the touch displacement resolution of the detection system. The primary magnification of the existing detection system is low, resulting in a low overall magnification, and it is difficult to further improve the resolution of the touch displacement. The FBG probe based on FBG Bending's micropore size measurement method cannot apply the main micro-touch displacement effect on the FBG, and the sensing signal converted into spectral information is weak, and the resolution of the system is very low.

2. The real-time performance of the detection system is poor, and it is difficult to realize precise online measurement. The detection method adopted by the National Institute of Standards and Technology must use a two-way area array CCD to receive signal images, and a more complex image algorithm must be used to achieve high-resolution monitoring of the displacement of the optical fiber measuring rod, which results in a large amount of data that the measurement system needs to process. The amount is greatly increased, which reduces the real-time performance of the detection system, and it is difficult to realize the synchronization between the small inner cavity size and the synchronization of the aiming signal and the start and stop measurement in the process of two-dimensional coordinate measurement.

3. There is coupling of two-dimensional radial touch displacement. The probe of the micropore size measurement method based on FBG Bending has the same performance in all directions, and there is coupling in the radial two-dimensional touch displacement sensing, and it cannot be separated, resulting in a large error in the two-dimensional measurement, and the radial two-dimensional measurement cannot be realized. Accurate measurement of touch displacement.

4. Does not have the decoupling capability of radial and axial detection. The detection methods mentioned above either do not have the ability to detect axially or do not have the ability to decouple radial and axial detection. When performing micro-scale measurements, the measurement steps are complicated and the measurement efficiency is low.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of low resolution and single measured dimension of the measurement method for tiny components in the prior art, and provide a device and method suitable for two-dimensional micro-scale measurement of tiny components. The needle is not only used as a touch sensing element, but also as a wavelength selection device of the fiber ring laser. When the end of the three-core fiber grating probe is affected by the touch displacement, the stress causes the parameters of the fiber grating to change, making the wavelength of the fiber ring laser The reflection center wavelength of the fiber grating of the selected device changes, and further changes the center wavelength of the output laser of the fiber ring laser. Due to the use of a saturable absorber to eliminate multi-longitudinal mode oscillation and suppress mode hopping, the single longitudinal mode narrow linewidth output of the fiber ring laser is realized. , so that the system has a higher sensitivity. Multi-channel optical switches are used to switch the channels for measuring fiber gratings to obtain the center wavelength information of the output laser of the corresponding fiber ring laser, and then perform differential data processing on it, which reduces the influence of temperature fluctuations on the measurement results and greatly improves the environmental protection of the device. The adaptability of the system enables a brand-new temperature-uncoupled two-dimensional microscale measurement.

The object of the present invention is achieved like this: a kind of three-core fiber grating probe micro-scale measuring device based on fiber ring laser, comprises by wavelength division multiplexer, erbium-doped optical fiber, circulator, coupler and isolator B successively connected The pumping source communicates with the annular cavity through the wavelength division multiplexer; the coupler communicates with the spectrum analyzer and the computer in turn through the isolator A; the multi-channel optical switch communicates with the circulator through the saturable absorber. The optical switch is connected to the three-core optical fiber through three single-mode optical fibers and the three-core optical fiber fan-out device, and the three-core optical fiber grating probe is fixed on the end of the three-core optical fiber through the probe holder; the computer is connected to the multi-channel optical switch The multi-channel optical switch is connected to the external reference grating; the three-core fiber grating probe and the external reference grating can be respectively used as wavelength selection devices of the fiber ring laser through the multi-channel optical switch switching.

A method for micro-scale measurement of a three-core fiber grating probe based on a fiber ring laser, the method is as follows: a pump source is used to provide pump light, and a wavelength division multiplexer enters an erbium-doped fiber as a gain medium to generate stimulated radiation Light, the stimulated radiation light is split by the coupler, and part of it is fed back to the annular cavity formed by sequentially connecting the wavelength division multiplexer, erbium-doped fiber, circulator, coupler and isolator B, and the other part is output as laser; The light in the ring cavity enters from the A port of the circulator, outputs through the B port, passes through a saturated absorber to eliminate multi-longitudinal mode oscillation and suppress mode hopping, and realizes the single longitudinal mode narrow linewidth output of the fiber ring laser, and then passes through as a wavelength selection After the three-core fiber grating probe or external reference grating of the device selects the frequency of the laser light, it is reflected into the B port, and then continues to transmit in the ring cavity after being output from the C port. With the continuous increase of the pump power, the spontaneous emission will be gradually suppressed , forming a narrow linewidth single longitudinal mode laser output; when the three-core fiber grating probe touches the component to be tested, the central wavelength of the reflection spectrum of the fiber grating in the three-core fiber grating probe will shift, thus changing Output laser wavelength, by switching multiple optical switches, using a spectrum analyzer to detect the center wavelength of the output laser when the three fiber gratings in the three-core fiber grating probe and the external reference grating are respectively used as wavelength selection devices; during data processing, when the three-core fiber grating When the two fiber gratings outside the center of the grating probe are used as the wavelength selection devices of the fiber ring laser, the output laser wavelength of the fiber ring laser is used for differential data processing, decoupling the one-dimensional radial touch displacement and temperature drift; when the three-core fiber grating probe When the fiber grating at the center of the needle and the external reference grating are respectively used as the wavelength selection device of the fiber ring laser, the output laser wavelength of the fiber ring laser is used for differential data processing, and the axial touch displacement without radial touch displacement and temperature drift coupling is obtained, realizing no Two-dimensional microscale measurements coupled with temperature.

The advantages of the present invention are:

1. The micro-scale measuring device and method of three-core fiber grating probe based on fiber ring laser has the characteristics of high precision, small contact force, no damage to the surface of the measured component, and long service life of the probe.

2. The fiber ring laser is used to generate a single longitudinal mode, narrow line width laser as the measurement light, the sensing and energy supply are integrated, the system is compact, and the measurement sensitivity is improved at the same time.

3. The optical detection signal is only transmitted inside the fiber grating, and the contact in space is converted into the change of the central wavelength of the reflection spectrum. When measuring micro-scale components, it is not affected by the shadowing effect of components. The measurement depth-to-diameter ratio can reach 100:1, satisfying The requirements for micro-scale measurement of microstructures with large aspect ratio are fulfilled.

4. The micro-scale measurement method of three-core fiber grating probe based on fiber ring laser can realize the coupling-free radial and axial measurements at the same time, which simplifies the steps of micro-scale measurement and improves the efficiency of micro-scale measurement.

5. A cross-reference differential compensation system is designed inside the probe, combined with a three-core fiber grating probe micro-scale measurement device method based on a fiber ring laser, which eliminates the impact of environmental temperature changes on the measurement and greatly improves the sensor's environmental protection. It can go deep into the space and environment where traditional measuring tools cannot work normally for precise measurement, such as narrow semi-enclosed spaces and flammable and explosive environments, and is also suitable for industrial on-site measurement.

Description of drawings

Figure 1 is a schematic diagram of the structure of a three-core fiber grating probe microscale measurement device based on a fiber ring laser;

Fig. 2 is the sectional view of A-A among Fig. 1;

Fig. 3 is the sectional enlarged view of three-core fiber grating probe in Fig. 1;

In the figure: 1. Pump source, 2. Wavelength division multiplexer, 3. Erbium-doped fiber, 4. Circulator, 5. Saturable absorber, 6. Multi-channel optical switch, 7. External reference grating, 8. Single Mode fiber, 9. Three-core fiber fan-out device, 10. Three-core fiber, 11. Probe holder, 12. Three-core fiber grating probe, 13. Computer, 14. Spectrum analyzer, 15a. Isolator A , 15b. Isolator B, 16. Coupler.

Detailed ways

The specific embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

A three-core fiber grating probe micro-scale measurement device based on a fiber ring laser, comprising a ring cavity formed by sequentially connecting a wavelength division multiplexer 2, an erbium-doped optical fiber 3, a circulator 4, a coupler 16 and an isolator B15b, The pumping source 1 communicates with the annular cavity through the wavelength division multiplexer 2; the coupler 16 communicates with the spectrum analyzer 14 and the computer 13 in turn through the isolator A15a; the multi-channel optical switch 6 communicates with the circulator 4 through the saturable absorber 5 The multi-channel optical switch 4 communicates with the three-core optical fiber 10 through three single-mode optical fibers 8 and the three-core optical fiber fan-out device 9, and the three-core optical fiber grating probe is fixed on the end of the three-core optical fiber 10 through the probe holder 11. The needle 12; the computer 13 communicates with the multi-channel optical switch 6; the multi-channel optical switch 6 is connected with the external reference grating 7; the three-core fiber grating probe 12 and the external reference grating 7 can be switched as optical fibers respectively Wavelength selective devices for ring lasers.

A method for measuring the microscale of a three-core fiber grating probe based on a fiber ring laser, the method is as follows: a pump source 1 is used to provide pump light, and a wavelength division multiplexer 2 enters an erbium-doped optical fiber 3 as a gain medium to generate Stimulated radiation light, the stimulated radiation light is split through the coupler 16, and a part of it is fed back to the annular cavity formed by sequentially connecting the wavelength division multiplexer 2, the erbium-doped optical fiber 3, the circulator 4, the coupler 16 and the isolator B15b, The other part is used as laser output; the light fed back into the ring cavity enters from the A port of the circulator 4, and is output through the B port and passes through the saturable absorber 5 to eliminate multi-longitudinal mode oscillation and suppress mode hopping, so as to realize the single longitudinal mode narrow of the fiber ring laser. Line width output, and then through the three-core fiber grating probe 12 as a wavelength selection device or the external reference grating 7 to select the frequency of the laser light, reflect into the B port, and continue to transmit in the ring cavity after being output from the C port. As the pump power continues to increase, the spontaneous radiation will be gradually suppressed to form a narrow linewidth single longitudinal mode laser output; The central wavelength of the reflected spectrum will shift, thereby changing the output laser wavelength, by switching the multi-channel optical switch 6, using the spectrum analyzer 14 to detect the three fiber gratings and the external reference grating in the three-core fiber grating probe 12 as wavelength selection respectively The output laser center wavelength of the device; in data processing, when the two fiber gratings outside the center of the three-core fiber grating probe 12 are respectively used as the wavelength selection device of the fiber ring laser, the output laser wavelength of the fiber ring laser is used for differential data processing and decoupling One-dimensional radial touch displacement and temperature drift; when the fiber grating at the center of the three-core fiber grating probe 12 and the external reference grating 7 are respectively used as the wavelength selection device of the fiber ring laser, the output laser wavelength of the fiber ring laser is differentially processed to obtain The axial touch displacement without radial touch displacement and temperature drift coupling realizes two-dimensional micro-scale measurement without temperature coupling.

The innovation and technical effect of the three-core fiber grating probe microscale measurement device and method based on fiber ring laser are: the three-core fiber grating probe is directly used as the wavelength selection device of the fiber ring laser, and the touch displacement information can be directly applied to the optical fiber. Ring laser, the wavelength of its output laser is changed, and a saturated absorber is used to narrow the output laser line width and make the fiber ring laser work in a single longitudinal mode. Compared with the traditional fiber grating sensor detection device, the present invention Sensitivity is greatly improved; in the present invention, three fiber gratings and external reference gratings in the three-core fiber grating probe as the sensor are also wavelength selection devices in the fiber ring laser at the same time, and the sensor and the sensor energy supply device are organically combined, and , under the control of the computer, the multi-channel optical switches switch the wavelength selective devices constituting the fiber ring laser respectively, and complete the two-dimensional touch displacement measurement without temperature coupling without adding additional optical devices, so that the present invention is more accurate than the traditional fiber grating The volume of the sensor detection device is more than doubled, and the cost is reduced by more than two times; the technical effect of the invention is outstanding.

Claims (2)

1. a kind of three-core fiber grating probe microscale measurement device based on fiber ring laser, it is characterized in that: by wavelength division multiplexer (2), erbium-doped optical fiber (3), circulator (4), coupler ( 16) and the isolator B (15b) are sequentially connected to form an annular cavity, and the pump source (1) communicates with the annular cavity through a wavelength division multiplexer (2); the coupler (16) is sequentially connected through the isolator A (15a) It communicates with the spectrum analyzer (14) and the computer (13); the multi-channel optical switch (6) communicates with the circulator (4) through a saturable absorber (5), and the multi-channel optical switch (6) passes through three single-mode optical fibers (8 ), the three-core optical fiber fan-out device (9) is connected with the three-core optical fiber (10), and the three-core optical fiber grating probe (12) is fixedly installed on the end of the three-core optical fiber (10) through the probe holder (11) The computer (13) is communicated with the multi-channel optical switch (6); the multi-channel optical switch (6) is connected with the external reference grating (7); the three-core fiber grating probe (12) passes through the external reference grating (7) The switching of multiple optical switches (6) can be respectively used as wavelength selection devices of fiber ring lasers. 2. a kind of three-core fiber grating probe micro-scale measurement method based on fiber ring laser, it is characterized in that: described method is as follows: utilize pumping source to provide pumping light, enter the doping as gain medium through wavelength division multiplexer The erbium fiber generates stimulated radiation light, and the stimulated radiation light is split by the coupler, and a part of the stimulated radiation light is fed back to the annular cavity formed by the sequential connection of the wavelength division multiplexer, the erbium-doped fiber, the circulator, the coupler and the isolator B, and the other part As a laser output; the light fed back into the ring cavity enters from the A port of the circulator, outputs through the B port, and passes through a saturable absorber to eliminate multi-longitudinal mode oscillation and suppress mode hopping, so as to realize the single longitudinal mode narrow linewidth output of the fiber ring laser , and then through the three-core fiber grating probe or external reference grating as a wavelength selection device to select the frequency of the laser, reflect it into the B port, and continue to transmit in the ring cavity after being output from the C port. With the continuous increase of the pump power, Spontaneous radiation will be gradually suppressed to form a narrow linewidth single longitudinal mode laser output; when the three-core fiber grating probe touches the component to be tested, the central wavelength of the reflection spectrum of the fiber grating in the three-core fiber grating probe will be Offset occurs to change the output laser wavelength. By switching multiple optical switches, use a spectrum analyzer to detect the central wavelength of the output laser when the three fiber gratings in the three-core fiber grating probe and the external reference grating are respectively used as wavelength selection devices; data processing In the above, when the two fiber gratings outside the center of the three-core fiber grating probe are respectively used as the wavelength selection devices of the fiber ring laser, the output laser wavelength of the fiber ring laser is used for differential data processing, decoupling the one-dimensional radial touch displacement and temperature drift; When the fiber grating in the center of the three-core fiber grating probe and the external reference grating are respectively used as the wavelength selection device of the fiber ring laser, the output laser wavelength of the fiber ring laser is used for differential data processing, and the axial direction without radial touch displacement and temperature drift coupling is obtained. Touch displacement to realize two-dimensional micro-scale measurement without temperature coupling.